Ultrasound imaging systems are a powerful tool for performing real-time imaging procedures in a wide range of medical applications. When performing standard imaging, ultrasound systems are typically operated in brightness-mode (commonly known as B-mode). When using B-mode to perform cardiac imaging, the motion of a heart beating can be viewed.
Traditionally, to measure the heart rate of an imaged heart, an ultrasound operator may select the system to be operated in motion-mode (commonly called M-mode). In M-mode, a single scan line is placed along an area of interest, and imaging along that one scan line is successively displayed along the X-axis over time. When there is motion along the scan line (e.g., when the scan line is placed so that it traverses the wall of a heart as it moves towards and away from the probe head), the resultant M-mode image appears as if it has a waveform that reflects the motion over time. A peak-to-peak measurement of this waveform can provide a heart rate measurement (after the sampling rate of the ultrasound image feed is taken into account).
M-mode may be cumbersome to use. For example, selecting the initial scan line and/or measuring the peak-to-peak distance may take time and expertise. As a result, there have been attempts to automate heart rate determination during B-mode imaging. These attempts typically involve automating manual M-mode processes. For example, in one scenario, a scan line is automatically selected and a time-series is generated over a series of frames at this scan line. A spectral analysis (such as a Fourier transform) is then performed on the data in the time-series to identify a frequency that may be reflective of the heart rate. Since this method relies on automated selection of a scan line, it may fail to capture motion in heart anatomical structures on areas of the image that do not intersect the scan line.
In another example, spatial points are identified on an image, and image data at these spatial points are plotted with respect to time. A Fourier transform may then be performed on the plotted image data to identify the heart rate. Since this method performs Fourier transform on the image data itself, it is similar to M-mode analyses and relies on plotted image data having a waveform appearance for the Fourier transform to accurately identify a frequency. However, such methods may not be sufficiently robust to determine a heart rate in situations where the image data at a selected spatial point plotted over time does not produce a waveform appearance (e.g., where a heart valve is present on a spatial point when it is closed, but not present on that spatial point when the heart valve is open, so that the resultant plotted image data over time does not produce a waveform).
There is thus a need for improved systems for determining a heart rate of an imaged heart in an ultrasound image feed. The embodiments discussed herein may address and/or ameliorate at least some of the aforementioned drawbacks identified above. The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings herein.